Open cell tray and method of foodstuff packaging

ABSTRACT

A packaging system includes a packaging member adapted to support a foodstuff in use. The packaging member includes a container or tray formed from an open celled material. The container or tray has an interior for contacting the foodstuff in use and an outside. The tray containing a foodstuff is wrapped in plastic and then placed in an oxygen barrier bag for evacuation, charging and sealing in a chamber to decrease the oxygen content in the barrier bag to prolong the shelf life of the foodstuff.

FIELD OF THE INVENTION

[0001] The present invention relates to packaging and is particularly, but not exclusively, relates to the packaging of foodstuffs, including meat products.

BACKGROUND

[0002] Controlled atmosphere packaging (CAP) based on low oxygen, is used to control meat colour so that when the meat is exposed to air-oxygen, it blooms to the correct red colour, to look fresh at the correct display time. A colour change of fresh meat is the most important factor in limiting its display shelf life. These meat colour changes do not occur when carbon monoxide (CO) is used in the preserving or flushing gas mix because it inhibits the formation of metmyoglobin. However because of its dangerous properties the use of CO is not always accepted in the meat industry.

[0003] Meat changes colour by the interaction of the myglobin and any oxygen. Please refer to the article entitled “Prevention of Transient Discoloration of Beef” as found in the Journal of Food Science vol 66, No. 3,2001 that is incorporated herein by reference in its entirety. The meat colour can change from blue(no oxygen, deoxymoglobin) to red(with oxygen oxymyoglobin) and to brown(iron oxydized metmyoglbin). For meat sale it is best to have red meat rather than brown or even blue meat. During CAP the oxygen content is controlled. The slower, the oxygen removal, the greater the use of the enzymes which are responsible for the metmyoglobin reduction and meat colour changes required while the meat pack is in the oxygen free environment. If too much enzyme activity has occurred during this storage time due to too much oxygen being present, on opening the bag, the meat will be slow to bloom and have a much shorter shelf life.

[0004] The meat colour is dependent of the oxidation state of the myoglobin. Metmyoglobin is the main pigment responsible for the discolouration of the meat. Residual oxygen in small quantities will form metmyoglobin (i.e. browning) which is then reduced to deoxymyoglobin i.e. MRA i.e. non-browning. This can be termed the browning curve. When the stored meat is removed from the bag, it blooms i.e. a red fresh colour is produced. However larger oxygen quantities will produce substantial amounts of metmyoblobin that cannot be reduced fully. This means the meat will be either brown, partially discoloured or discolour quicker once on the shelf. Large residual oxygen quantities require oxygen scavengers. As indicated in the paper even when substantially low oxygen levels are achieved this storage system still requires a minimum of 2-4 days to allow the metmyoglbin reduction. This length of time is not commercially economic. Therefore our client has improved the systems and oxygen scavengers so as to not only allow the solid trays, as described in the article (see reference), to be used, but also open cell foam trays that are known to entrap oxygen. Therefore the aim is to have very low initial oxygen levels and then reduce them still further during storage, to reduce the likelihood of the formation of the browning. Also if the oxygen is removed quickly then there can be less chance of any residual oxygen to form metmyoglobin (the browning), therefore there would be more potential for MRA activity to be used later on and less need for oxygen scavengers which in turn then means an extended shelf life. This has been proven by applicant's tests and actual commercial application.

[0005] In summary, as shown by the most relevant prior art, i.e. U.S. Pat. No. 6,054,153 to Carr and U.S. Pat. No. 6,210,725 to Columbo and U.S. Pat. No. 4,926,614 (Assigned to Securefresh Pacific Limited) that are incorporated herein by reference in their entirety, the difference between Carr and Colombo is very small but important. Both cover CAP with solid foam trays. However Carr talks about gas flushing and an activated oxygen scavenger, and Colombo talks about a valve in a barrier bag, solid carbon dioxide and a vacuum to flush the oxygen out. As disclosed, these systems are relatively slow and the trays retain residual oxygen that effects the meat colour. Their systems require several weeks of cold storage to allow the MRA i.e. metmyoglobin reducing activity) to work and also a substantial amount of the MRA is used up during this time which in turn reduces the shelf life when opened.

[0006] In contrast, the contribution of our client's invention to the art, is the provision of a rapid reduction in oxygen in the meat which results in less enzyme use. This system produces the cheapest CAP having the longest shelf life with the best meat colour when exposed to air-oxygen. The Securefresh invention achieves this, by a new combination of features for a controlled atmosphere package that, in particular, includes a pressure chamber having a snorkel and venting, with an open celled foam tray and a rapid oxygen scavenger. The oxygen scavenger is not an activated oxygen scavenger nor is a vented bag used.

[0007] One of the aims when packaging foodstuffs, especially fresh meat products and the like, is to remove as much oxygen from the package as possible; in fact ideally, to provide an oxygen-free environment therein. Oxygen allowed to remain in contact with the foodstuff can result in the foodstuff deteriorating as it provides an environment in which undesirable micro-organisms may proliferate. Systems are known which help address this issue. Such systems often involve the evacuation of air from the package and the subsequent charging of the package with an inert atmosphere gas such as carbon dioxide. The carbon dioxide acts as a bacteriostat. A problem with such systems is that there may be a residual amount of oxygen left in the cells of the packaging materials themselves (e.g. polystyrene foamed plastic trays).

OBJECT OF THE INVENTION

[0008] It is an object of the present invention to provide packaging or a packaging system which will obviate or minimise the foregoing disadvantages in a simple yet effective manner or which will at least provide the public with a useful choice.

STATEMENT OF INVENTION

[0009] Accordingly in one broad aspect of the present invention there is provided a packaging system for storing oxygen sensitive foodstuff including:

[0010] An open celled tray for holding the foodstuff;

[0011] A plastics material over-wrapping or lidding the tray to form a covered tray having an enclosed space for the foodstuff;

[0012] The plastics material having micro-perforations;

[0013] A chamber having at least one vent and snorkel;

[0014] The over-wrapped or lidded tray and foodstuff being enclosed in an oxygen barrier bag;

[0015] The barrier bag being enclosed in the chamber;

[0016] wherein the normal atmosphere within the barrier bag and chamber is quickly evacuated, followed by charging with gas followed by sealing such that the oxygen content within the over-wrapped or lidded tray is less than 200 ppm.

[0017] Preferably an oxygen absorbent sachet is placed within the bag before sealing.

[0018] Preferably the open celled tray has an outer layer of solid material to retain foodstuff liquid.

[0019] Accordingly in a second aspect of the present invention there is provided a method of packaging oxygen sensitive foodstuff comprising the steps of:

[0020] Providing a vented chamber having a snorkel, at least one over-wrapped or lidded tray containing a foodstuff and an oxygen barrier bag.

[0021] Placing at least one over-wrapped or lidded, open celled tray into the barrier bag.

[0022] Placing the barrier bag in the chamber.

[0023] Evacuating both the chamber and bag via a chamber snorkel to reach vacuum level as per the vapour pressure of the foodstuff product whereby the increase in pressure inside the bag ensures the bag is expanded and because of the expanding vapour coming off the product (meat) the oxygen is displaced and a very low partial pressure of oxygen is left inside the barrier pouch.

[0024] Injecting gas into the bag and simultaneously venting the chamber to the atmosphere so no undue pressure is placed on the bag.

[0025] Sealing the bag.

[0026] Preferably after sealing the bag, the chamber is opened and the bag is removed.

[0027] Preferably after bag removal, the bag can be transported or stored until the covered foodstuff is or are required to be removed from the barrier bag and displayed.

[0028] Preferably an oxygen absorbent sachet is placed within the barrier bag before sealing.

[0029] The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features, and where specific integers are mentioned herein which has known equivalents in the art or which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 shows a cross section of the tray packaging member.

[0031]FIG. 2 shows a cross section of the SECUREPAK™ machine of U.S. Pat. No. 4,926,614.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0032] One embodiment of the present invention will now be described with reference to the accompanying drawing in which FIG. 1 is a diagrammatic cross-section of a packaging member.

[0033] The following is a description of the preferred embodiments of the invention, given by way of example only. It will be appreciated that a variety of changes and modifications may be made to these examples, and a range of other embodiments are possible, within the general scope of the invention.

[0034] The present invention relates to containers or receptacles for foodstuffs to be packaged, and related packaging systems, and may be incorporated into any standard foodstuff packaging method being compatible with standard known foodstuff, packaging apparatus and machinery. In addition, the invention may be used in the packaging of a variety of different foodstuffs including meat and cheeses for example.

[0035] Within this specification the word “package” is used to describe the packaging, which may be comprised of a number of separate components that interact in use, which substantially surrounds the foodstuff in use. For example, a tray on which foodstuff is supported which has been over-wrapped with a suitable membrane may be referred to as a package. Alternatively, the pouch that contains a number of individually wrapped trays having foodstuff thereon may also be considered a package. Those of general skill in the art will realise other examples of packages that fall within the scope of the present invention.

[0036] In FIG. 1 a packaging member is provided which may be in the form of a tray 1 of the kind commonly used to pack and display meat and the like; having a base 2 on which the foodstuff to be packed is supported in use and a lip 3 projecting at an angle therefrom around the perimeter of the base 2 which acts to help contain the product. Thus the tray 1 described is in the form of a shallow dish. The tray 1 is constructed of material commonly used in the foodstuffs industry; for example, a plastics material compatible with the packing of foodstuffs. The tray is constructed substantially of a layer 5 of an open cell plastic material with a thin layer of solid material 6 on an underside thereof. The open celled construction on the surface of the tray 1 supporting the foodstuff allows liquid to be absorbed into the tray and the thin layer of solid material 6 on the underside of the tray 1 acts to retain the liquid therein. The outer solid layer 6 may be about 100 microns to about 200 microns thick. The inner solid layer 7 must allow oxygen evacuation therethrough, and, for example, may be from about 15 microns thick to 30 microns thick. The principal purpose of this layer is to stiffen the construction.

[0037] The layer 5 of the open celled material is preferably open celled polystyrene. The layers of solid material may be styrene.

[0038] In use, the foodstuff, fresh meat for example, will be placed on the tray and the tray then over-wrapped with a web of covering or wrapping membrane 4. It will be appreciated that the covering is generally made of a clear plastic material but may be made of any other suitable material. In this preferred form of the invention the covering is perforated, preferably micro-perforated, to ensure gas equilibration between enclosed regions of the over-wrapped tray and the outside ambient atmosphere. One tray, or a number of similarly wrapped trays, may then be placed within a pouch or outer barrier bag (not shown) that is evacuated of normal atmosphere, which contains 20.9% oxygen to an atmosphere containing 300 ppm oxygen or less. This evacuation is used by a SECUREPAK™ machine as disclosed by patent U.S. Pat. No. 4,926,614, and then charged with carbon dioxide or other inert atmosphere gas capable of substantially preserving the foodstuff (nitrogen, or suitable mixtures, for example). The pouch is then sealed and the packaged foodstuff may be stored at an appropriate temperature and/or transported for sale. Oxygen in the open celled layer 5 will be substantially removed during the evacuation process. The rate of evacuation of air and charging with carbon dioxide or other suitable inert atmosphere gas may be altered according to the packaging system being employed, the size of the package and the like.

[0039] It will be appreciated that, if desired, the material from which the pouch or outer barrier bag is made may contain an oxygen absorbent material. For example, the material must have minimal oxygen permeability; foil laminates, metallicized films and high barrier plastic films. In addition, the sealing of the pouch must be effective so as to ensure a stable gaseous environment within the package and in particular to ensure the invasion of oxygen is inhibited. Alternatively, standard methods may be used, for example, placing an oxygen absorbent sachet in the pouch or outer barrier bag.

[0040] It will be appreciated by those of general skill in the art that following storage and transportation of meat packaged according to the present invention the pouch may be opened with a resultant bloom time of 20 to 30 minutes.

[0041] The present invention may have the advantage of helping to increase the shelf life of packed meat. For example, under ideal conditions (held at approximately—1.5° C.) fresh lamb may be stored for twenty weeks with no adverse affects on the meat. Similarly, it may be displayed chilled in a store environment for four days.

[0042] The main features of the inventions modified atmosphere package are:

[0043] 1. Place over-wrapped or lidded, vented open cell trays into a barrier pouch/bag.

[0044] 2. Place barrier pouch in Securepak™ machine having a snorkel.

[0045] 3. Position open end of barrier pouch over snorkel.

[0046] a. Start machine cycle.

[0047] i. Chamber comes down

[0048] ii. Barrier pouch is clamped over snorkel.

[0049] iii. Evacuation takes place in both chamber and inside barrier pouch (via snorkel).

[0050] iv. Vacuum level reaches vapour pressure of product (E.g. Meat at 0° C. at sea level is approximately 6 millibars).

[0051] v. Vapour comes off the product (meat) in the barrier pouch. This causes the pressure in the barrier pouch to be slightly more than the pressure in the chamber even though the same vacuum source is used. This all happens because as the moisture on the surface of the product (meat) turns to vapour it expands more than 400 times its volume.

[0052] vi. The increase in pressure inside the barrier pouch ensures the pouch is expanded and because of the expanding vapour coming off the product (meat) the oxygen is displaced and a very low partial pressure of oxygen is left inside the barrier pouch.

[0053] vii. Gas (carbon dioxide or other) is injected into the pouch and simultaneously the outer chamber is vented to atmosphere so no undue pressure is placed on the barrier pouch.

[0054] viii. The barrier pouch is hermetically sealed.

[0055] ix. The chamber is opened and the barrier pouch is removed. 

What we claim is:
 1. A packaging system for storing oxygen sensitive foodstuff comprising: an open celled tray for holding the foodstuff; a plastic material over-wrapping or lidding the tray to form a covered tray having an enclosed space for the foodstuff, the plastics material having micro-perforations; a chamber having at least one vent and snorkel; and an oxygen barrier bag for enclosing the over-wrapped or lidded tray and foodstuff, said barrier bag being enclosable in the chamber, wherein a normal atmosphere within the barrier bag and chamber is evacuatable, the barrier bag is chargable with gas and sealable so that the oxygen content within the over-wrapped or lidded tray is less than 200 ppm.
 2. A packaging system as claimed in claim 1 further comprising an oxygen absorbent sachet sealable within the barrier bag.
 3. A packaging system as claimed in claim 2 wherein the open celled tray has an outer layer of solid material to retain foodstuff liquid.
 4. A method of packaging oxygen sensitive foodstuff comprising the steps of: placing at least one over-wrapped or lidded, open celled tray containing a foodstuff into an oxygen barrier bag; placing the barrier bag in a vented chamber having a snorkel; evacuating both the chamber and the barrier bag via the snorkel to reach a vacuum level corresponding to a vapour pressure of the foodstuff so that a pressure inside the barrier bag increases to ensure that the barrier bag is expanded, and so that vapour coming off the foodstuff is expanding and displacing the oxygen in the barrier bag so that a very low partial pressure of oxygen is left inside the barrier bag; injecting gas into the barrier bag and simultaneously venting the chamber to atmosphere so that no undue pressure is placed on the barrier bag; and sealing the barrier bag.
 5. The method of packaging foodstuffs as claimed in claim 4 further comprising the steps of opening the chamber after said sealing the barrier bag step and then removing the barrier bag from the chamber.
 6. The method of packaging foodstuffs as claimed in claim 5 further comprising the step of transporting the barrier bag.
 7. The method of packaging foodstuff as claimed in claim 5, further comprising the step of storing the barrier bag until the foodstuff is required to be removed from the barrier bag and displayed.
 8. The method of packaging foodstuffs as claimed in claim 6 further comprising the step of placing an oxygen absorbent sachet within the barrier bag before said sealing the barrier bag step. 